A probe card is a device used to couple signals to and from bonding pads of integrated circuits during testing before the integrated circuits have been packaged. With reference to FIGS. 1-3, the probe card 10 includes a printed circuit board 12, a mounting shelf 14 formed of an insulative material, such as epoxy, and two sets of probe needles 16a, b supported by the mounting shelf 14. The probe needles 16a, b in each set extend inwardly toward each other beneath an aperture 18 formed in the printed circuit board 12. Each of the probe needles 16 terminate in respective tips 20 that are adapted to make contact with respective bonding pads of an integrated circuit (not shown) during testing. The end of each probe needle 16 opposite its tip 20 is connected to a respective contact terminal 22 by an electrical trace 23 that is adapted to be coupled to a test equipment (not shown).
For the probe card to be effective, the precise position of the tip 20 of each needle 16 must be adjusted in three-dimensions to be within some predefined tolerance of a respective desired tip location. The predefined tolerances are very tight due to the extremely small feature sizes of microelectronic devices. The current techniques for adjusting the position of the tip 20 involve a long, detailed, time consuming, and error prone process. In the current method, the probe card 10 is first mounted on a support plate of a clamshell-shaped motherboard fixture (not shown). The probe card 10 is secured in place by a retaining plate which is pivotally mounted to the support plate. The downward pressure of the retaining plate flexes the probe needles 16 in a similar fashion to the way the probe needles 16 are flexed when used in testing microelectronic devices. The probe card 10 is mounted in the motherboard fixture (not shown) with the probe needles 16 facing inward such that the probe needles are proximate to a chuck driven inspection plate (not shown) within the motherboard fixture. The inspection plate includes a pair of concave windows and a pair of isolation dots. The inspection plate is positionable in three-dimensional space with respect to the probe needles. The chuck driven inspection plate is capable of producing a visual feedback of the two-dimensional position of a needle tip 20 with respect to a desired tip location. The inspection plate can apply mechanical force to the probe needles 16 which simulates the mechanical force applied to the probe needles when the probe needles are used to inspect a microelectronic device. The inspection plate is also capable of providing feedback related to the third dimension of the position of the needle tip 20 with respect to the desired tip location. This is accomplished by detecting the completion of an electrical circuit which is defined by the physical contact between the probe needle tip and an electrical contact formed at the isolation dot on the inspection plate.
The adjustment and maintenance of probe cards 10 currently requires a highly skilled technician, who adjusts the position of each needle tip 20 on a trial-and-error basis. Since the probe card 10 is generally mounted in the motherboard fixture with its probe needles 16 facing inwardly, the technician must view and manipulate the probe needles 16 through an aperture 18 formed in the printed circuit board 12, manually adjusting the position of each needle tip 20 with a pair of tweezers or the like. After adjusting the position of several needle tips 20, the accuracy of the adjustments must be ascertained with the inspection plate. The inspection plate is positioned proximate the probe card 10 to determine whether each of the adjusted tips is within the predefined tolerance of its desired location. The inspection system displays on a monitor (not shown) the two dimensional position of each of the needle tips 20 relative to its respective desired tip location. Third dimension information is communicated by an indication of whether a circuit has been completed. After viewing the results, the inspection plate is positioned away from the probe card 10 to allow the technician to continue adjusting the tip positions. A highly skilled technician may take upwards of five tries to position a needle tip 20 within the predefined tolerance. Each time the needle tips are manually adjusted, the inspection plate must be positioned proximate the probe card 10 to retest the tip position. Adjusting the needles 16 through the aperture 18 in the printed circuit board 12 is quite awkward. It can take a skilled technician several hours to adjust the positions of all the needle tips 20 on a single probe card 10.
Use of the probe card 10 during testing microelectronic devices causes the needle tips 20 to move out of their desired tip locations. Therefore, the adjustment procedure must be performed continually over the life of the probe card. This requires the use of highly-skilled technicians and requires a great deal of time and effort to be spent on maintaining the probe card.